Sadržaj, sastav i osobine humusa kraljevačkog pseudogleja pod različitim načinom korišćenja i primenjenim meliorativnim merama

Abstract

U radu su prikazani rezultati određivanja sadržaja, sastava i osobina humusa kraljevačkog pseudogleja u pet profila koji reprezentuju tri različita varijeteta prema načinu njegovog korišćenja i to šumski (1), livadski (2) i njivski (3), pri čemu je otvaranje izvršeno na neđubrenoj, đubrenoj sa NPK i đubrenoj sa NPK+Ca varijanti. Određivanje frakcionog sastava humusa vršeno je metodom Kononove i Beljčikove, a sadržaj ugljenika u zemljištu ekstraktima i huminskim kiselinama bihromatnom metodom Tjurina u modifikaciji Simakova. Optička gustina i prag koagulacije (izoelektrična tačka) huminskih kiselina određivani su postupcima po Kononovoj. Najvećim sadržajem humusa 5,83 % karakteriše se šumski varijetet, potom livadski sa 3,00 %, njivski neđubreni 1,79 %, đubreni 1,57 % i đubreni + Ca 1,52 %. Preovlađivanje fulvo nad huminskim kiselinama u širokom intervalu (Chk/Cfk 0,35-0,98), izuzimajući njivski varijetet đubreni+Ca (Chk/Cfk, 1,50-2,80) je bitna karakteristika frakcionog sastava humusa ispitivanih varijeteta pseudogleja. Visoko preovlađivanje huminskih kiselina slobodnih i vezanih mobilnim R2O3, nad huminskim kiselinama vezanim sa Ca, u humusnom i eluvijalnom horizintu šumskog i livadskog varijeteta, njihova signifikantna dominacija u humusnom horizontu njivskog, veoma izražena u humusnom i eluvijalnom horizontu njivskog sa NPK i skoro potpuno izjednačenje ovih frakcija u njivskom sa NPK+Ca, takođe je jedna od bitnih karakteristika humusa. Udeo humina varira u dijapazonu od 40,3 do 65,8 %. Prema odnosu ekstinkcija E4:E6, najmanju kondenzovanost aromatskih jezgara huminskih kiselina ima šumski (5,67), povoljniju njivski (5,00-5,17) varijeteti, a najpovoljniju (4,64) livadski varijetet pseudogleja. Vrednosti praga koagulacije, odnosno izoelektrične tačke, huminskih kiselina (16-20 meq. CaCl2 na 1/l humata) ukazuju na visok stepen njihove disperznosti i uniformnosti.

The paper encompasses the results on contents, compositions and properties of humus determined in pseudogley of the Kraljevo area in five profiles that represent three different types according to their mode of utilisation: 1) forest soil type, 2) meadow soil type and 3) arable field soil type. The opening of the profiles was performed on unfertilised soil, soil fertilised with NPK (120:120:80) and soil fertilised with NPK + 5,000 kg Ca fertiliser ha-1. On the basis of the obtained results it was established that the highest humus content had been detected in the forest soil (5.83%), followed by the meadow soil (3.00%), while the lowest humus content had characterised the unfertilised arable field soil (only 1.79%). The decreasing tendency of the humus content in arable field types of soil fertilised with NPK (1.57%) and NPK + Ca fertiliser (1.52%) has been continued, indicating an improvement of the conditions for organic matter mineralisation, as well as a necessity of the humisation application, together with mineral fertilisation and calcification of pseudogley soils in order to maintain and improve their adsorptive complex. An important characteristic of a humus fraction composition in investigated soil types, except in arable field soil with incorporated Ca fertiliser, is prevailing fulvo over humic acids, which may be observed from the ratio Chk/Cfk, that range from 0.35 to 0.98, with the highest participation of fulvo acids in unfertilised arable field soil. In the arable field variety with incorporated Ca fertiliser, this ratio changed drastically down to the depth of 45 cm, varying within the range of 1.50-2.80, which indicated a stabilising character of the processes caused by the incorporated Ca and a decrease in humic acid mobility by formation of corresponding humates. On the basis of the extinction ratio E4:E6, it was determined that the lowest (5.67), i.e. highest (4.64) degree of humic acid condensation, i.e. of their aromatic nuclei condensation, was present in the forest soil, i.e. the meadow soil, respectively. The determination of coagulation threshold, i.e. of the isoelectric point, of humic acids indicates a high degree of their dispersion and uniformity in that aspect considering that complete coagulation is achieved by utilisation of 16-20 m.eq CaCl2 per 1 l of humate.